Three-dimensional modelling of multilayered asphalt concrete pavement structures: strain responses and permanent deformation

In any given asphalt concrete (AC) pavement structure, the permanent deformation (PD) in each AC layer has an influence and contributes differently to the total pavement rutting. The degree of influence will generally vary as a function of the AC modulus and layer thickness. Presently, most of the AC material/layer PD characterisation and analyses are based on laboratory and/or field testing in combination with stress-strain modelling under assumed circular and uniformly distributed wheel loading. In this paper, a three-dimensional finite element program, ANSYS, incorporating measured vertical tyre–pavement contact pressure (TPCP) was utilised for computing the PD of each AC layer with different variables such as the AC layer modulus, AC layer thickness, TPCP levels, vertical wheel loads, and tyre inflation pressure. A strain energy concept was also proposed for evaluating the PD rate and contribution of each AC layer. The corresponding results indicated the following: (1) the PD contribution of each AC layer varies as a function of the AC modulus as theoretically expected; (2) the intermediate AC layer significantly contributes to lateral deformation; however, both the intermediate and top AC layers significantly contribute to vertical PD; (3) the AC layer thickness and the magnitude of the lateral TPCP hardly influence the PD of the intermediate AC layer; (4) the PD influence of small light trucks can be quite substantial depending on the loading conditions and cannot be neglected in the analysis of this nature; (5) the distribution of the TPCP has a very significant influence on the PD of the top AC layer and is more pronounced as the TPCP gets more non-uniformly distributed.